Firstborn Weigh More, Study

July 28, 2016

According to a new study, firstborn women are more likely to be overweight or obese than their younger siblings. The results of this study mimic earlier research that found the same risk among firstborn males.

The reasons for this are unknown at this time, but one theory has to do with the blood vessels in a woman’s uterus during her first pregnancy. Narrower blood vessels could lead to a lower energy supply to the baby in utero, causing firstborns to metabolize food and regulate weight differently as adults later in life.

Other research has shown that eldest children also have an increased risk for reduced insulin sensitivity—leading to type 2 diabetes—and high blood pressure. The combination of these factors also increases the risk for heart disease. Another study showed that firstborns have higher rates of hay fever and food allergies as well.